1. Field of the Invention
This invention pertains to the field of straight chain haloalkyl phosphate compounds and to polymeric compositions containing said phosphate compounds as a flame retardant preservative.
2. Description of the Prior Art
Both tris(2,3-dibromopropyl)phosphate and tris(2-chloroethyl)-phosphate are well known, commercially used flame retardants. Tris-(2-chloroethyl)phosphate combines the good qualities of low cost and low viscosity. The low viscosity of tris(2-chloroethyl)phosphate allows for the easy handling and pumping of said flame retardant for incorporation into a polymerization reaction. The low viscosity of tris(2-chloroethyl)phosphate also results in a more thorough mixing and, thus, more uniform distribution of said flame retardant in the polyurethane. The use of tris(2-chloroethyl)phosphate is limited by the fact that it is volatile because of its low molecular weight and thus migrates from the polymer causing a loss of permanent flame retardancy. Furthermore, tris(2-chloroethyl)-phosphate lacks thermal and hydrolytic stability causing the degradation of foams having said flame retardant incorporated therein and equipment exposed thereto.
Tris(2,3-dibromopropyl)phosphate, on the other hand, is both more thermally and more hydrolytically stable than tris(2-chloroethyl)phosphate and has sufficient molecular weight to prevent major losses through volatility. However, tris(2,3-dibromopropyl)-phosphate is a highly viscous liquid which is difficult to handle and process.
A novel class of compounds has been discovered which combines the greater hydrolytic and thermal stability as well as the lower volatility of tris(2,3-dibromopropyl)phosphate with the lower viscosity of tris(2-chloroethyl)phosphate while eliminating the undesirable properties of the above prior art compounds, i.e., the bis(2,3-dibromopropyl)-chloroalkyl phosphates within the scope of this invention possess a greater hydrolytic and thermal stability as well as a lower volatility than tris(2-chloroethyl)phosphate while also possessing a significantly lower viscosity than tris-(2,3-dibromopropyl)phosphate.